Different types of digital systems may employ different communication formats. For example, high-speed memory systems may utilize different signaling rates, voltages, impedances, common-mode signaling levels, termination structures (such as ground-referenced common-mode signaling levels) and communication formats than other memory systems. The nature of different communication formats makes it difficult to support support multiple formats on a single interface circuit, particularly where the formats in question diverge in driving voltage, currents and signaling rates. Furthermore, as digital components continue to decrease in die size, there is a trend to simplify pin counts and the number of input and output signals. Consequently, designers tend to design digital components (especially microprocessors and controllers and the like) in a manner dedicated to a single communications format.
Hence, there is a need to reduce costs and otherwise improve the marketability of digital components by enabling them to adapt to multiple communication formats without substantially increasing pin count, and without requiring platform-specific designs. This need also exists in the field of memory, where is desired to produce memory components that can support communication parameters for diverse systems.
Note that like reference numerals refer to corresponding parts throughout the drawings.